Oxidation of hydrocarbons



Patented Dec. 24, 1940 UNITED STATES OXIDATION or nrnnocsanoms WilliamH. m, New Orleans, 1..., and Clyde 0. Sheely, State College, Miss.

Original application April 2, 1938, Serial No.

199,636. 1939, 8erial No. 286,815

Divided and this application July :6,

1 Claim. (Cl. 260-451) This invention relates to a new and improvedprocess for the preparation of chemical compounds by the oxidation ofaliphatic hydrocarbons in the presence of a catalyst, and more par- 5ticularly to such a process wherein the reaction products comprisealiphatic alcohols, aldehydes and acids.

This application is a continuation-in-part of our copending applicationSerial No. 108,478, filed October 30, 1936, now Patent No. 2,190,453,and

is a division of our copending application Serial No. 199,636, fliedApril 2, 1938.

The higher aldehydes of the aliphatic series have considerable value aschemical compounds and a number of them have found use in industry asperfumes. The difliculties in the way of preparing such compounds,however, have kept their costs so high as to limit their field ofusefulness. An improved and simpler method of obtaining such aldehydeswould make more accessible a very desirable class of products. The samecondition holds in the case of a number of the higher aliphatic alcoholsand acids also, for example those containing in the neighborhood of 8 to12 95 carbon atoms.

An object of our invention is an improved method for the production ofalcohols, aldehydes, and acids by the incomplete oxidation of allphatichydrocarbons. A further object is such a process in which carefullycontrolled conditions allow a high degree of efliciency in thepreparation of the desired products. A still further object is a processin which the several products obtained may be separated in relativelypure form. Additional object will be disclosed as the process is furtherdescribed hereinafter.

We have found that the foregoing objects may be accomplished by theprocess of our invention which comprises introducing a normally liquidhydrocarbon in the vapor phase into a heated chamber, together with anoxidizing agent comprising a gas containing free oxygen. The oxidationstep is carried out in the presence of benzoyl peroxide as a catalyst.Within the reaction chamber the mixed gases and vapors are subjected toa temperature between 250 and 500 C. While the oxidation of thehydrocabons constitutes an exothermic reaction, the heat evolved willnot be suflicient to maintain the desired temperature and externalheating will be necessary. It is essential that the reactionperiod bekept at a relatively short time interval, and we have found 15 secondsto be the maximum allowable time. Preferably we employ a reaction period86 not greater than 12 seconds, in order that the oxidation may notproceed too far. The reacting materials and reaction products areremoved from the heated chamber while still in the vapor phase and are.condensed by any desired method and apparatus under such conditions andin such 6 an atmosphere that further reaction cannot take place. Theamount of hydrocarbon will be above the explosive limit in all cases. Wehave found it desirable to use an amount of hydrocarbon of at least 10%by volume of the gaseous reaction mix- 10 ture, and preferably between20 and 40%.

It will be a desirable step in our process also to utilize the unreactedhydrocarbon resultin from the process and to recycle it to an additionalsimilar oxidation step, whereby the ad- I. vantages of the presence ofan excess of hydrocarbon are obtained with no loss in non-reactingmaterial.

The accompanying drawing shows diagrammatically a flow sheet of onemethod of carrying Q out our process. From a reservoir i, the normallyliquid hydrocarbon is forced through conduit 2 into the preheater 3. Thegas containing free oxygen is passed through conduit 4 through thepreheater 3, en route to the reaction chamas her 5. Both the vaporizedhydrocarbon and the oxygen containing gas pass into the reaction chamber5 where they become intimately mixed and where a temperature of 250 to500 C. is maintained, vjsaid catalyst, promoting partial go oxidation,being present, whereby partial oxidation of the hydrocarbons is broughtabout. The vapors pass out the conduit 6 into separator l, where any tarformed in the process is separated out. The mixed vapors and gases thenpass as through condenser 8, where the products capable of condensationbecome liquefied. The liquid condensate flows into reservoir 9, while asecond vessel l0 receives any further condensed product not caught inchamber 9, but condensed in ii. The reservoirs 9 and it contain theliquefied unreacted hydrocarbon that has passed through the process, andalso condensed water and the alcohols, aldehydes and acids resultingfrom the oxidation process. Such alcohols, aldehydes and acids willcommonly be found in the water-insoluble layer.

Specific operating conditions suitable for our process for theproduction of alcohols, aldehydes, and acids are shown in the followingexample. 50 This is to be considered as merely illustrative, however,and not limiting in its application.

Example One gram of benaoyl peroxide was dissolved in u Momoinaphtha.Thismixturewasvaporised intheusuaimannerandmixedwithairata temperatureoi 887' C. The time oi reaction wassfisecondsandthepercentageoi'hydrocarbon in the reaction mixture was 18.7. Theyield was approximately 16.84% aldehydes and 14.15% acids.

The method of operation according to the present invention producesalcohols, aldehydes and acids. However, it is especially i'avorable tothe production oi alcohols. The alcohols, aldehydes and acids resultingfrom the oxidation oi hydrocarbons according to the process of ourinvention, are products 01' considerable economic value and 01'desirable properties, and the process described oii'ers a novel andadvantageous method of obtaining such products. Our process ischaracterized by higher yields and greater efliciency than any processin the art.

The alcohols, aldehydes and acids may be separated from the hydrocarboncondensate and from one mother by the use of suitable solvents. In thecase of aldehydes, for example, a saturated solution oi. sodiumbisulflte was found desirable for extraction, the bisulflte subsequentlybeing made alkaline and beins subjected to steam distillation. The acidswere desirably extracted by h orio acid.

Whileourprocesshaabeendescribedindetail in the foregoing, it will beunderstood that many variations in procedure may be employed withoutdeparting from the scope of our invention. In the example cited, ahydrocarbon traction oi a speciilo distillation range was used, but itwould be a highly desirable procedure also to start with a singlealiphatic hydrocarbon, ior example octane, or a mixture of octanes.

We wish to be limited, therefore, only by the following patent claim:

The process for producing partially oxidized products or normally liquidaliphatic hydrocarbons which comprises introducing said hydrocarbons invapor phase, tosether with an oxidizing agent comprising a gascontaining tree oxygen, into a reaction chamber at a temperature between250 C. and 500 C., maintaining the amount of hydrocarbon in thehydrocarbon-oxygen ratio above the explosive limit, and reacting saidmaterials for a period not exceeding 15 seconds in the presence ofbenzoyl peroxide.

WILLIAM H. ICING. CLYDE Q. BHEELY.

